Chickens could be right, because if it was a singular answer it would be "lays" eggs. Oviposit means to lay eggs but there is no animal with this name. The Platypus is the only mammal to lay eggs, but then it would be lays eggs......?
A mammal has mammary glands that produce mlik if supplied with the correct hormone, of course - hence only females at certain times. The other characteristic is that all mammals have hair.
Crocodiles are reptiles - this can also be defined